1. Field of the invention
The present invention relates to a method for producing multilayer panels from an extrudable plastic, in which method two strips of plastic, delivered by extruders, are joined together, with a material therebetween, by means of an arrangement of rolls. The invention also relates to an apparatus for the implementation of such a method.
2. Description of the Prior Art
U.S. Pat. No. 4,448,739 discloses a method of this kind, and an apparatus for the implementation thereof, comprising a single roller-smoothing machine having an extruder arranged on each side. Before entering the first roll-gap or rip, the material is applied to one of the rolls over a predetermined angular distance and is then introduced into 20 the gap in the roll-arrangement jointly with the first strip from the extruder. After this first gap, the textile material is fixed to the surface of the first strip, the other strip of plastic being fed to the roller-smoothing machine only in another gap. The material is in the form of a cloth or fabric which is wound upon a roller and, during the manufacture of multilayer strips or panels, is fed to the arrangement of rolls. Because of the weave of the cloth or fabric, the weft- and warp-threads are in a predetermined spatial association with each other and the patterns or structures woven into the textile material are visible to an observer from the outside after they have been placed between the strips of plastic in the panel thus made of transparent plastic. Prefabricated patterns and structures must be acceptable and, during the manufacture of multilayer panels, there is no way of influencing the relative positions of the individual threads of the textile material.
German OS No. 22 00 594 discloses a method for producing moulded articles. In this case a glass mat, or individual loose threads, are placed between strips of thermoplastic synthetic materials. Moreover, two glass mats, at least one of which has been previously impregnated with a thermoplastic resin, may be joined together by means of rolls under the action of heat. Sheets produced by this method, and reinforced with glass fibres, are passed, at a specific temperature, to a shaping device in order to obtain the desired moulded article. The glass fibres serve to reinforce the moulded article and they are embedded in the plastic irregularly with no preferential direciton. The fibres are relatively short and are in no regular or predetermined geometrical arrangement in relation to each other.